Effect of hydroxy group activity on the hydrogel formation temperature of β-cyclodextrins and its application in profile control

Abstract

In order to increase the gelling temperature of β-CD-based hydrogels and expand the application range of β-CD-based hydrogels in oil reservoirs, glycidyl ethers with different chain lengths were prepared for modification of β-CDs, and then the modified β-CD was chemically crosslinked with epichlorohydrin (EPI) to prepare hydrogels. Thus, the gelling temperature of β-CD hydrogels was successfully increased from 65 to 125 °C. FTIR, 1H NMR, XRD and DSC were used to investigate the mechanism of the changing of gelling temperature. The results showed that the long chain alkyl changed the electron cloud density on the β-CD ring, increased the difficulty of hydroxyl group leaving, thus increased the gel forming temperature. Furthermore, the swelling behavior and the core plugging performance of the gel were evaluated. The results indicated that the maximum swelling rate of modified β-CD gel was 75 %. The core displacement experiment showed that the plugging rate was greater than 95 %, the unplugging rate was greater than 90 %, and the maximum breakthrough pressure of water flooding reached 7.43 MPa. These results indicated the practical value of β-CD hydrogels in high temperature (60–125 °C) oil fields.